build(deps): update coverage requirement from ==7.7.* to ==7.8.* in /requirements (#381)

build(deps): update coverage requirement in /requirements

Updates the requirements on [coverage](https://github.com/nedbat/coveragepy) to permit the latest version.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](coveragepy/coveragepy@7.7.0...7.8.0)

---
updated-dependencies:
- dependency-name: coverage
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
(cherry picked from commit 8c3a41a)

Author: dependabot[bot]

requirements/_tests.txt

@@ -1,5 +1,5 @@
 coverage ==7.2.7; python_version < '3.8'
-coverage ==7.7.*; python_version >= '3.8'
+coverage ==7.8.*; python_version >= '3.8'
 pytest ==7.4.3; python_version < '3.8'
 pytest ==8.3.*; python_version >= '3.8'
 pytest-cov ==6.0.0